The Thin Film Transistor-Liquid Crystal Display (TFT-LCD) is formed by a pixel array defined by gate lines and data lines extended in a horizontal direction and a vertical direction respectively. When the TFT-LCD displays an image, a gate driver inputs a square wave in a certain width to each row of pixels via a corresponding gate line from top to bottom sequentially so as to activate the row of pixels, and then a source driver inputs signals required by each row of pixels to the corresponding row of pixels from top to bottom via the data lines sequentially. The higher the resolution is, the more the output signals of the gate driver and the source driver of the display are, and thus the length of the driving circuit is increased, which is disadvantageous for a bonding process of the module driving circuit.
To address the above issues, a circuit design of Gate Driver on Array (GOA) is generally employed in the manufacture of the existing displays, wherein a gate switching circuit of TFTs is integrated on an array substrate of a display panel to achieve a scanning and driving function for the display panel, so that a bonding area for the gate driving circuit and a space for periphery wiring can be omitted, thus achieving a symmetrical structure of both sides and an aesthetic design of narrow bezel of the display panel.
In a design of GOA circuit adopting the Low Temperature Poly-Silicon (LTPS) technology, a GOA circuit of Complementary Metal Oxide Semiconductor can be employed, wherein the TFTs of P type and the TFTs of N type together form an integrated circuit of complementary type. Therefore, characteristics of the TFTs of P type and the TFTs of N type need to be ensured in the procedure of manufacturing the circuit, thus increasing complexities and difficulties of the LTPS process, reducing performance and a yield rate of the TFTs, and in turn increasing production cost.
In order to reduce the production cost, a GOA circuit of MOS transistors of single type is adopted in the existing technology. A GOA unit circuit of NMOS LTPS as illustrated in FIG. 1 possesses features of uni-directional scan (OUT_n−1), a pulling-up control (making a signal output terminal OUT_n output a high level), a uni-directional direct-current pulling-down (pulling-down the signal output terminal OUT_n to a low level) and the like. However, the scope to which the GOA circuit of uni-directional scan can be applied is relatively narrow; moreover, the signal output terminal OUT_n of the GOA circuit is pulled down to the low level only when the transistor M01 is turned on. As a result, when the transistor M01 is turned off in error due to an interference signal, it is impossible to pull down the signal output terminal OUT_n. Thus, reliability of the GOA circuit is decreased in such uni-directional pulling-down manner. Further, two clock signals CLK and CLKB are adopted to drive the above GOA circuit of MOS transistors of single type, and thus, in one operational period of the GOA circuit, there are only two clock signals CLK and CLKB being used to drive the GOA circuit; therefore, a large external driving capability is required for the GOA circuit, causing power consumption of the circuit to be increased and lifespan of the GOA circuit to be reduced.